Bridge



FREDK. HARBACK, 0F PITTSFIELD, MASSACHUSETTS.

BRIDGE.

Specification of Letters Patent No. 4,694, dated August 12, 1846.

To @ZZ whom t may concern:

-Be it known that I, FREDERICK of Pittsfield, in the count-y of Berkshire and State of Massachusetts, have invented a new and useful Improvement in` Truss-v Frames for Bridges, Roofs, 8:6.; andI do hereby declare that the same is fully de' scribed and represented in the following speciication and accompanying drawings,-

the truss a cylindrical tubular post I I, ma)r letters, figures, and references thereof.

Of said drawings Figure l exhibits a lon-j gitudinal elevation of my improved truss' frame; Fig. 2, a longitudinal and vertical:y elevation of a part of it, taken through one?,

of the beams of either the top or bottom cords; Fig. 3, a top view-of a part of the bottom cord, and saddle or stirrup, at the junction of the braces and suspension bolts or rods. Fig. 4 is a bottom view ofpart of said bottom cord, exhibiting one of the counter stirrups on which the lower beams of the lower cord 'restf- Fig. 5 is a transverse section taken throughone end of the vertical suspension rods of the truss.

In my improved truss frame I make use of hollow metallic cylindrical beams, for all or any of the main cords, and braces, and counter braces. The said beams being made in the shape of cylinders, can be manufactured so as to combine great strength and stiffness. Although I consider the adoption of such to constitute a great improvement in trusses for bridges, etc., I make use in connection therewith of another of much importance, and by so doing obtain a truss frame whose capability to resist vertical strains far exceeds that of any combination of like character of which I am aware is now in use.

A B, Fig. 2, is the top cord or stringer, composed of two parallel cast iro-n or other proper metallic tubular beams, each of which is made in sections which are conneet-ed together, by lapped joints (one of which is seen at K), or in any other convenient and proper manner. Y

C D is the lowercord similarly constructed of two parallel tubular beams made of boiler wrought iron plates riveted together, in the manner of those of steam boilers. E E E &c..are the principal braces and F F F the counter diagonal braces all made of cylindrical tubes of wrought or cast iron and each cast with a toe piece, a, at each end of it and projecting from opposite sides of it as seen in the drawing.

HARBACK,

G G, are the vertical suspension bolts ori..

rods, which pass down through the cords, and toe `pieces of the braces, and counter braces. They are placed three abreast with four screw nuts, b, c', d, e', upon each,

( as seen in Fig. 2) and the said bolts Vconi nect the cords or stringere and at the same time c online the braces and counter braces, in their proper positions. At each end of be inserted between lthe top and bottom cords in order to aid in keeping them at their proper distances apart` I I, &c., denote/"metallic saddles suitably shaped to receive and support the cords which rest against them. In connection with the'said stirrups counter stirrups or saddles'I I are disposed withvrespect to the cords and made to fit them as seen in Fig. 5. The ends of the braces and counter braces, rest in contact with saddles I I their positions thereon being insured by projections f f raised upon the saddles, the toes of the braces abutting against the said projections. The stirrups and saddles serve as safeguards to prevent the cords from being crushed, or flattened, by the action of the screw bolts and nuts; the toe pieces of the diagonal -braces being made to receive the suspension bolts, G G, through them to be conlined to the stirrups land saddles by screws and screw nuts, placed upon the bolts as seen in the drawings. By conining the toe pieces of each diagonal brace and counter brace directly to the saddle I, I, by supplementary screws and screw nuts upon the bolts I convert the said brace and counter brace into a suspension brace, and counter brace as well as a thrust brace and counter brace; that is to say I enable them to act by tension as well as thrust.

In what is known as Howes patent bridge which consists of diagonal braces, abutting blocks and tension rods, the braces act by thrust only. They in no respect operate by tension or as suspension braces.

By combining with the braces, and counter braces, the toe pieces and with the tension rods the supplementary screws and nuts as above described, I effect a very important improvement in such a bridge truss, as the braces and counter braces may thus be made to act as suspension or tension, as well as thrust braces, and thus to resist the vertical strains upward as Well as downward.

. In railway viaducts this is a very important -beams and claim the right to usesuch in al bridge' it will be evident that other arrange- Vments or constructions of beams may be used, and therefore I do not confine myself strictly 'to the proportions of thevarious parts as expressed in the drawings nor to the material or materials as above set forth but intend to vary such as circumstances l"Inay'requirerwhile I maintain an analogous combination or combinations of them. I do not therefore claim as my invention the combination of diagonal thrust braces and counter braces (which Yact by thrust only) and vertical suspension rods, but

That which I do claim as my improvement thereon consists in-V A combination of devices by which the diagonal braces operate either by thrust or tension, at pleasure, while the vertical rods atthe same time operate either by tension or thrust; the said combination, by which this peculiarity is derived Vbeing composed of the attachments of the diagonal braces and counter braces, and upper and lowerstring ers-#together with the double sets of nuts upon the vertical rods, one set being above and the other being below each Stringer-,fthe whole beingV substantially as hereinbefore speciied.

` In testimony whereof I have 'hereto set Asignature this eighth day of June A D.

,Y FREDERICK HARBACK,

Witnesses:`

JAMES D.AC0LT, S. A. WRIGHT. 

